Ferromagnetic-particle manufacturing apparatus

ABSTRACT

A ferromagnetic-particle manufacturing apparatus includes: a single mode cavity that resonates with a microwave of a predetermined wavelength; a microwave oscillator electrically connected to the single mode cavity and configured to introduce the microwave of a predetermined wavelength into the single mode cavity; a pipe disposed to pass through an inside of the single mode cavity, the pipe being formed of a dielectric material; a pump configured to introduce, from one end of the pipe, an alkaline reaction liquid containing metal ions of a ferromagnetic metal; an impedance measuring device configured to measure an impedance of the single mode cavity; and a pump-flowrate deciding unit configured to decide, based on a measurement result of the impedance measuring device, a pump flowrate by which the impedance of the single mode cavity becomes a predetermined value or more; wherein the pump is configured to introduce the reaction liquid at the pump flowrate decided by the pump-flowrate deciding unit; and wherein ferromagnetic particles are generated by reacting the reaction liquid.

TECHNICAL FIELD

The present invention relates to a ferromagnetic-particle manufacturingapparatus.

BACKGROUND ART

Due to magnetic properties, ferromagnetic particles (nanoparticles) arerecently used as active pharmaceutical ingredients for a magneticresonance imaging method (MRI), a drug delivery system (DDS), a localhyperthermia treatment and so on.

JP2006-28032A discloses a method of generating magnetite particles,which are one type of such ferromagnetic particles, by using acoprecipitation reaction. Specifically in this method, a predeterminedamount of ferrous chloride (FeCl₂) solution and a predetermined amountof ferric chloride (FeCl₃) solution are put into a reaction container.While the solutions are heated and stirred in the reaction container,sodium hydroxide (NaOH) solution is added thereto. Thus, acoprecipitation reaction between ferrous ions (Fe²⁺) and ferric ions(Fe³⁺) occurs so that magnetite (Fe₃O₄) particles are generated.

In such a conventional method, when magnetite particles are industriallyproduced in large volume, a great amount of reaction liquid is stirredin a reaction container. In this case, the reaction liquid is likely tovary in temperature and a mixed condition of the reaction liquid islikely to be non-uniform, which makes it difficult to improve generationefficiency of magnetite particles. There is another problem in that thethus generated magnetite particles tend to vary widely in compositionand dimension.

In addition, in the manufacture of active pharmaceutical ingredients,regulations related to production control and quality control on medicaldrugs and medical devices, i.e., the GMP (Good Manufacturing Practice)must be observed in general. To be specific, for example, a reactionliquid is required to be maintained in an aseptic condition withoutbeing reacted with an outside air. However, in the conventional methodin which a reaction liquid is stirred in a reaction container, it isdifficult to comply with the GMP.

SUMMARY OF THE INVENTION

In view of the above disadvantages, the present invention has been madefor efficiently solve the same. The object of the present invention isto provide a ferromagnetic-particle manufacturing apparatus capable ofefficiently manufacturing ferromagnetic particles.

The present invention is a ferromagnetic-particle manufacturingapparatus including: a single mode cavity that resonates with amicrowave of a predetermined wavelength; a microwave oscillatorelectrically connected to the single mode cavity and configured tointroduce the microwave of a predetermined wavelength into the singlemode cavity; a pipe disposed to pass through an inside of the singlemode cavity, the pipe being formed of a dielectric material; and a pumpconfigured to introduce, from one end of the pipe, an alkaline reactionliquid in which metal ions of a ferromagnetic metal and hydroxide ionsare dissolved; wherein ferromagnetic particles are generated by reactingthe reaction liquid.

According to the present invention, the reaction liquid introduced fromthe one end of the pipe is heated by the microwave in the single modecavity, so that the reaction of the reaction liquid is promoted and thusferromagnetic particles are generated. When ferromagnetic particles aregenerated in the pipe, the thus generated ferromagnetic particles andthe microwave are magnetically coupled. Thus, a rate of a reflected waverelative to an incident wave of the microwave decreases, so that animpedance of the single mode cavity increases. In this case, bymeasuring the impedance in the single mode cavity, a productionefficiency of ferromagnetic particles in the pipe can be easilyestimated from outside. In addition, according to the present invention,ferromagnetic particles are continuously generated in the pipe, withoutneed for stirring the reaction liquid in a reaction container. Thus, thereaction liquid is unlikely to vary in temperature and a mixed conditionof the reaction liquid is unlikely to be non-uniform, so that variationof the generated ferromagnetic particles in composition and dimension issmall. In addition, it is easy to observe the GMP.

Preferably, the ferromagnetic-particle manufacturing apparatus furtherincludes: an impedance measuring device configured to measure animpedance of the single mode cavity; and a pump-flowrate deciding unitconfigured to decide, based on a measurement result of the impedancemeasuring device, a pump flowrate by which the impedance of the singlemode cavity becomes a predetermined value or more; wherein the pump isconfigured to introduce the reaction liquid at the pump flowrate decidedby the pump-flowrate deciding unit. In this embodiment, due to theapplication of the aforementioned principle of impedance elevation, aproduction efficiency of ferromagnetic particles is improved. That is tosay, as the pump flowrate increases, a generation efficiency offerromagnetic particles also increases until the pump flowrate reaches acertain threshold value. In accordance therewith, the impedanceincreases. However, at a pump flowrate beyond the threshold value, anunreacted reaction liquid outflows from the other end of the pipe, whichin turn decreases the generation efficiency of ferromagnetic particles.In accordance therewith, the impedance decreases. Thus, in thisembodiment, since the pump-flowrate deciding unit decides a pumpflowrate by which the impedance becomes a predetermined value or more,and the reaction liquid is introduced from the one end of the pipe atthe flowrate decided by the pump-flowrate deciding unit, a productionefficiency of ferromagnetic particles can be maintained at a desiredlevel or more.

Specifically, for example, an axial length of the pipe is 20 mm to 200mm.

In addition, the present invention is a ferromagnetic-particlemanufacturing apparatus includes: an induction heating coil; aradiofrequency power source electrically connected to the inductionheating coil and configured to form an alternating field inside theinduction heating coil; a pipe being disposed to pass through the insideof the induction heating coil, in which at least a partial area of thepipe in an axial direction thereof is formed of a dielectric materialand an area, which is nearer to one end of the pipe than the area formedof a dielectric material, is formed of a conductive material; and a pumpconfigured to introduce, from the one end of the pipe, an alkalinereaction liquid in which metal ions of a ferromagnetic metal andhydroxide ions are dissolved; wherein ferromagnetic particles aregenerated by reacting the reaction liquid.

According to the present invention, the area of the pipe, which isformed of a conductive material, is induction-heated by the alternatingfield inside the induction heating coil, and the reaction liquidintroduced from the one end of the pipe is heated by the heat generatedby the area formed of a conductive material, so that the reaction of thereaction liquid is promoted and thus ferromagnetic particles aregenerated. When ferromagnetic particles are generated in the pipe, thethus generated ferromagnetic particles function as a core (magneticcore) in the area of the pipe, which is formed of a dielectric material.Thus, the inductance of the induction heating coil increases, so thatthe impedance of the induction heating coil increases. In this case, bymeasuring the impedance of the induction heating coil, a productionefficiency of ferromagnetic particles in the pipe can be easilyestimated from outside. In addition, according to the present invention,ferromagnetic particles are continuously generated in the pipe, withoutneed for stirring the reaction liquid in a reaction container. Thus, thereaction liquid is unlikely to vary in temperature and/or a mixedcondition of the reaction liquid is unlikely to be non-uniform, so thatvariation of the generated ferromagnetic particles in composition anddimension is small. In addition, it is easy to observe the GMP.

Preferably, the ferromagnetic-particle manufacturing apparatus furtherincludes: an impedance measuring device configured to measure animpedance of the induction heating coil; and a pump-flowrate decidingunit configured to decide, based on a measurement result of theimpedance measuring device, a pump flowrate by which the impedance ofthe induction heating coil becomes a predetermined value or more;wherein the pump is configured to introduce the reaction liquid at thepump flowrate decided by the pump-flowrate deciding unit. In thisembodiment, due to the application of the aforementioned principle ofimpedance elevation, a production efficiency of ferromagnetic particlesis improved. That is to say, as the pump flowrate increases, ageneration efficiency of ferromagnetic particles also increases untilthe pump flowrate reaches a certain threshold value. In accordancetherewith, the impedance increases. However, at a pump flowrate beyondthe threshold value, an unreacted reaction liquid outflows from theother end of the pipe, which in turn decreases the generation efficiencyof ferromagnetic particles. In accordance therewith, the impedancedecreases. Thus, in this embodiment, since the pump-flowrate decidingunit decides a pump flowrate by which the impedance becomes apredetermined value or more, and the reaction liquid is introduced fromthe one end of the pipe at the flowrate decided by the pump-flowratedeciding unit, a production efficiency of ferromagnetic particles can bemaintained at a desired level or more.

Specifically, for example, an axial length of the area of the pipe,which is formed of a conductive material, is 20 mm to 200 mm.

In addition, specifically, for example, the metal ions of theferromagnetic metal are either or both of iron ions and nickel ions. Forexample, magnetite particles as ferromagnetic particles are generatedfrom an alkaline reaction liquid, in which ferrous ions and ferric ionsare dissolved, by means of the coprecipitation reaction between theferrous ions and the ferric ions. In addition, nickel ferrite particlesas ferromagnetic particles are generated from an alkaline reactionliquid, in which ferric ions and nickel ions are dissolved, by means ofthe coprecipitation reaction between the ferric ions and the nickelions.

In addition, specifically, for example, sodium hydroxide is dissolved inthe reaction liquid.

In addition, specifically, for example, an internal diameter of the pipeis 0.3 mm to 5.0 mm.

Preferably, an inner surface of the pipe is treated with a corrosionprotective covering. Glass and various synthetic resins, such aspolyethylene, polypropylene and fluorine resin, may be used as acovering material. Polyolefin such as polyethylene and polypropylene ispreferred, and polypropylene is particularly preferred. According tothis embodiment, smoothness to a reaction liquid flowing through thepipe can be maintained all the time.

The pump-flowrate deciding unit or respective elements of thepump-flowrate deciding unit can be realized by a computer system.

In addition, a program for executing them in the computer system and acomputer-readable storage medium storing the program are also thesubject matters of the present invention.

Herein, the storage medium includes one that can be recognized byitself, such as a flexible disc, and a network in which various signalsare transmitted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structural view showing a ferromagnetic-particlemanufacturing apparatus in a first embodiment of the present invention.

FIG. 2 is a schematic structural view showing a ferromagnetic-particlemanufacturing apparatus in a second embodiment of the present invention.

MODES FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described in detailherebelow with reference to the attached drawings.

FIG. 1 is a schematic structural view showing a ferromagnetic-particlemanufacturing apparatus in a first embodiment of the present invention.

As shown in FIG. 1, a ferromagnetic-particle manufacturing apparatus 10in this embodiment includes: a single mode cavity 11 that resonates witha microwave of a predetermined wavelength; a microwave oscillator 12electrically connected to the single mode cavity 11 and configured tointroduce the microwave of a predetermined wavelength into the singlemode cavity 11; a pipe 13 disposed to pass through the inside of thesingle mode cavity 11, the pipe 13 being formed of a dielectricmaterial; and pumps 14 a and 14 b configured to introduce, from one endof the pipe 13, an alkaline reaction liquid in which metal ions of aferromagnetic metal and hydroxide ions are dissolved.

The single mode cavity 11 is a hollow container made of a conductivewall such as a metal, and is also referred to as cavity resonator. Thesingle mode cavity 11 is configured to resonate with a microwave of apredetermined wavelength which is specified depending on a size, a shapeand a mode of the single mode cavity 11. Namely, inside the single modecavity 11, only the microwave of a predetermined wavelength can exist asa standing wave. To be specific, for example, the single mode cavity 11has a parallelepiped shape having a length of 150 mm in a right and leftdirection (z direction), a length of 109.2 mm in an up and downdirection (y direction), and a length of 54.5 mm in a directionperpendicular to a sheet plane (x direction) in FIG. 1. In a TE10 modein which a microwave is transmitted in the z direction, the single modecavity 11 is configured to resonate with a microwave having a wavelengthof 120 mm.

The microwave oscillator 12 is electrically connected to the single modecavity 11 through a coaxial cable 17, and is capable of introducing themicrowave of a predetermined wavelength into the single mode cavity 11.

The pipe 13 in this embodiment is a resin pipe of a cylindrical shape.To be specific, for example, an internal diameter of the pipe 13 is 0.3mm to 5.0 mm, and an axial length thereof is 20 mm to 200 mm. A materialof the pipe 13 is, e.g., polyvinyl chloride.

As shown in FIG. 1, the pipe 13 coaxially passes through the inside ofthe single mode cavity 11, with an axis of the pipe 13 being oriented inparallel to the z direction of the single mode cavity 11. An innersurface of the pipe 13 is treated with a corrosion protective covering,so that smoothness to a liquid flowing through the pipe 13 is maintainedall the time. Glass and various synthetic resins, such as polyethylene,polypropylene and fluorine resin, may be used as a covering material.Polyolefin such as polyethylene and polypropylene is preferred, andpolypropylene is particularly preferred.

In this embodiment, as shown in FIG. 1, a first liquid tank 31 isliquid-tightly connected to the one end of the pipe 13 via the pump 14 aassociated with the first liquid tank 31, and a second liquid tank 32 isliquid-tightly connected to the one end of the pipe 13 via the pump 14 bassociated with the second liquid tank 32.

The first liquid tank 31 accommodates a metal salt solution containingmetal ions of a ferromagnetic metal. To be specific, for example, metalions of the ferromagnetic metal are either or both of iron ions andnickel ions. In this embodiment, an iron salt solution, in which ferrouschloride (FeCl₂) and ferric chloride (FeCl₃) are dissolved in a molarratio of 1:2, is accommodated in the first liquid tank 31.Alternatively, an iron salt solution, in which ferrous sulfate (FeSO₄)and ferric sulfate (Fe₂(SO₄)₃) are dissolved in a molar ratio of 1:1,may be accommodated in the first liquid tank 31.

On the other hand, the second liquid tank 32 accommodates an alkalinesolution containing hydroxide ions. To be specific, for example, analkaline solution in which sodium hydroxide (NaOH) is dissolved isaccommodated in the second liquid tank 32.

The pumps 14 a and 14 b in this embodiment are configured to introduce amixed liquid (hereinafter referred to as reaction liquid), in which theiron salt solution accommodated in the first liquid tank 31 and thealkaline solution accommodated in the second liquid tank 32 are mixed,is introduced from the one end of the pipe 13 such that a molar flowrateof ferrous ions (Fe²⁺), ferric ions (Fe³⁺) and hydroxide ions (OH⁻) is1:2:8.

The ferromagnetic-particle manufacturing apparatus 10 in this embodimentfurther includes an impedance measuring device 15 that measures animpedance of the single mode cavity 11, and a pump-flowrate decidingunit 16 that decides, based on a measurement result of the impedancemeasuring device 15, a pump flowrate by which the impedance of thesingle mold cavity 11 becomes a predetermined value or more.

In this embodiment, as shown in FIG. 1, the impedance measuring device15 is electrically connected to the coaxial cable 17, and is configuredto measure the impedance of the single mode cavity 11 through thecoaxial cable 17.

The pump-flowrate deciding unit 16 is specifically formed of, e.g., acomputer system including a storage unit storing a control program orthe like. The storage unit of the pump-flowrate deciding unit 16 isconfigured to previously store a target value of the impedance of thesingle mode cavity 11. As described below, the target value may bedecided based on, e.g., a measurement result change of the impedancemeasuring device 15 with respect to a pump flowrate change.

In addition, the pump-flowrate deciding unit 16 is configured to decide,based on a measurement result of the impedance measuring device 15, apump flowrate (pump flowrate set value) by which the impedance of thesingle mode cavity 11 becomes the previously stored target value ormore. Each of the pumps 14 a and 14 b is configured to introduce thereaction liquid from the one end of the pipe 13 at the pump flow rate(pump flowrate set value) decided by the pump-flowrate deciding unit 16.

Next, an operation of the embodiment as described above is described.

Firstly, an alkaline reaction liquid, in which ferrous ions (Fe²⁺),ferric ions (Fe³⁺) and hydroxide ions (OH⁻) are dissolved in a molarratio of 1:2:8, is introduced from the one end of the pipe 13 by thepumps 14 a and 14 b. In addition, a microwave of a predeterminedwavelength (e.g., 120 mm) is introduced from the microwave oscillator 12into the single mode cavity 11.

The reaction liquid flowing through the pipe 13 is heated by themicrowave introduced into the single mode cavity 11 up to a reactiontemperature (e.g., 40° C. to 80° C.). Thus, reaction of the reactionliquid is promoted and a coprecipitation reaction between the ferrousions (Fe²⁺) and the ferric ions (Fe³⁺) occurs, whereby magnetite (Fe₃O₄)particles are generated. The thus generated magnetite particles aremoved by a pressure of the reaction liquid flowing through the pipe 13so as to be taken out from the other end of the pipe 13.

When the magnetite particles are generated in the pipe 13, the magnetiteparticles and the microwave are magnetically coupled. Thus, a rate of areflected wave relative to an incident wave of the microwave decreases,so that an impedance of the single mode cavity 11 increases. Theimpedance of the single mode cavity 11 is measured by the impedancemeasuring device 15.

The pump-flowrate deciding unit 16 reads out a measurement result fromthe impedance measuring device 15, and compares the measurement resultwith the previously stored target value.

When the measurement result is equal to or larger than the target value,the flowrate of each of the pumps 14 a and 14 b at this time is decidedas the aforementioned pump flowrate set value.

On the other hand, when the measurement result is smaller than thetarget value, the measurement result is stored in the pump-flowratedeciding unit 16, and the pumps 14 a and 14 b are controlled such thatthe flowrate of the reaction liquid introduced into the the one end ofthe pipe 13 increases.

In principle, as the pump flowrate increases, a generation efficiency ofmagnetite particles also increases until the pump flowrate reaches acertain threshold value. In accordance therewith, the impedance of thesingle mode cavity 11 increases (case 1). However, as the pump flowrateincreases after exceeding the threshold value, an unreacted reactionliquid outflows from the other end of the pipe 13, which in turndecreases the generation efficiency of magnetite particles. Inaccordance therewith, the impedance of the single mode cavity 11decreases (case 2).

The pump-flowrate deciding unit 16 reads out a measurement result fromthe impedance measuring device 15, and compares the measurement resultwith the stored previous measurement result.

When the current measurement result is larger than the stored previousmeasurement result, the situation is judged as the case 1, and the pumps14 a and 14 b are controlled such that the flowrate of the reactionliquid introduced to the one end of the pipe 13 gradually increases.During this operation, the pump-flowrate deciding unit 16 successivelyreads out measurement results from the impedance measuring device 15,and compares the measurement results with the previously stored targetvalue. At a time when one of the measurement results becomes the targetvalue or more, the pump-flowrate deciding unit 16 decides each of theflowrates of the pumps 14 a and 14 b as the aforementioned pump flowrateset value.

On the other hand, when the current measurement result is smaller thanthe stored previous measurement result, the situation is judged as thecase 2, and the pumps 14 a and 14 b are controlled such that theflowrate of the reaction liquid introduced to the one end of the pipe 13gradually decreases. During this operation, the pump flow rate decidingunit 16 successively reads out measurement results from the impedancemeasuring device 15, and compares the measurement results with thepreviously stored target value. At a time when one of the measurementresults becomes the target value or more, the pump-flowrate decidingunit 16 decides each of the flowrates of the pumps 14 a and 14 b as theaforementioned pump flowrate set value.

Then, each of the pumps 14 a and 14 b is set such that the reactionliquid is introduced from the one end of the pipe 13 at the pumpflowrate (pump flowrate set value) decided by the pump-flowrate decidingunit 16. Thus, magnetite particles are hereafter generated in the pipe13 at a desired generation efficiency or more corresponding to theimpedance target value previously stored in the pump-flowrate decidingunit 16.

According to the above embodiment, the reaction liquid introduced fromthe one end of the pipe 13 is heated by the microwave in the single modecavity 11, so that the reaction of the reaction liquid is promoted andthus ferromagnetic particles are generated. When ferromagnetic particlesare generated in the pipe 13, the thus generated ferromagnetic particlesand the microwave are magnetically coupled. Thus, a rate of a reflectedwave relative to an incident wave of the microwave decreases, so that animpedance of the single mode cavity 11 increases. In this case, bymeasuring the impedance in the single mode cavity 11, a productionefficiency of ferromagnetic particles in the pipe 13 can be easilyestimated from outside.

In addition, according to this embodiment, ferromagnetic particles arecontinuously generated in the pipe 13, without need for stirring thereaction liquid in the reaction container.

Thus, the reaction liquid is unlikely to vary in temperature and themixed condition of the reaction liquid is unlikely to be non-uniform, sothat variation of the generated ferromagnetic particles in compositionand dimension is small. In addition, it is easy to observe the GMP.

In addition, in this embodiment, due to the application of theaforementioned principle of impedance elevation, a production efficiencyof ferromagnetic particles is improved. That is to say, as the pumpflowrate increases, a generation efficiency of ferromagnetic particlesalso increases until the pump flowrate reaches a certain thresholdvalue. In accordance therewith, the impedance increases. However, at apump flowrate beyond the threshold value, an unreacted reaction liquidoutflows from the other end of the pipe, which in turn decreases thegeneration efficiency of ferromagnetic particles. In accordancetherewith, the impedance decreases. Thus, in this embodiment, thepump-flowrate deciding unit 16 decides a pump flowrate by which theimpedance becomes a predetermined value or more. Since the reactionliquid is introduced from the one end of the pipe 13 at the flowratedecided by the pump-flowrate deciding unit 16, a production efficiencyof ferromagnetic particles can be maintained at a desired level or more.

Next, a second embodiment of the present invention is described withreference to FIG. 2.

FIG. 2 is a schematic structural view showing a ferromagnetic-particlemanufacturing apparatus in a second embodiment of the present invention.

As shown in FIG. 2, in place of the single mode cavity 11, the microwaveoscillator 12 and the pipe 13 formed of a dielectric material of theferromagnetic-particle manufacturing apparatus 10 in the firstembodiment, a ferromagnetic-particle manufacturing apparatus 20 in thesecond embodiment includes: an induction heating coil 21; aradiofrequency power source 22 electrically connected to the inductionheating coil 21 and configured to form an alternating field inside theinduction heating coil 21; and a pipe 23 disposed to pass through theinside of the induction heating coil 21. At least a partial area 23 a ofthe pipe 23 in an axial direction thereof is formed of a dielectricmaterial. An area 23 b, which is nearer to one end of the pipe 2 thanthe area 23 a formed of a dielectric material, is formed of a conductivematerial.

The induction heating coil 21 is a solenoid coil having a cylindricalshape. For example, a diameter of the induction heating coil 21 is 20mm, and an axial length thereof is 150 mm.

The radiofrequency power source 22 is electrically connected to theinduction heating coil 21 through a radiofrequency cable 27, and iscapable of supplying an alternating current of a predetermined frequency(e.g., 20 kHz) to the induction heating coil 21 so as to form analternating field inside the induction heating coil 21.

The pipe 23 in this embodiment is formed by coaxially connecting a resinpipe 23 a having a cylindrical shape, and a metal pipe 23 b having acylindrical shape that has the same internal diameter as that of theresin pipe 23 a. To be specific, for example, an axial length of theresin pipe 23 a is 20 mm to 200 mm, and an axial length of the metalpipe 23 b is 20 mm to 200 mm. The internal diameters of the resin pipe23 a and the metal pipe 23 b are both 0.3 mm to 5.0 mm. A material ofthe resin pipe 23 a is, e.g., polyvinyl chloride, while a material ofthe metal pipe 23 b is e.g., stainless.

As shown in FIG. 2, the pipe 23 is coaxially passes through the insideof the induction heating coil 21, with an axis of the pipe 23 beingoriented in parallel to an axis of the induction heating coil 21. Afirst liquid tank 31 is liquid-tightly connected to the one end of thepipe 23 on the side of the metal pipe 23 b via the pump 14 a associatedwith the first liquid tank 31, and a second liquid tank 32 isliquid-tightly connected to the one end of the pipe 23 on the side ofthe metal pipe 23 b via the pump 14 b associated with the second liquidtank 32. An inner surface of the pipe 23 is treated with a corrosionprotective covering, so that smoothness to a liquid flowing through thepipe 23 is maintained all the time.

In this embodiment, as shown in FIG. 2, an impedance measuring device 15is incorporated in the radiofrequency power source 22, and is configuredto measure an impedance of the induction heating coil 21. In general,the commercially available radiofrequency power source 22 incorporatesthe impedance measuring device 15. However, when the radiofrequencypower source 22 that does not incorporate the impedance measuring device15 is used, the impedance measuring device 15 may be located outside theradiofrequency power source 22.

A pump-flowrate deciding unit 16 in this embodiment is configured topreviously store a target value (predetermined value) of the impedanceof the induction heating coil 21.

The other structure is substantially the same as that of the firstembodiment shown in FIG. 1. In FIG. 2, the same part as that of thefirst embodiment is shown by the same reference number, and detaileddescription thereof is omitted.

Next, an operation of the embodiment as described above is described.

Firstly, an alkaline reaction liquid, in which ferrous ions (Fe²⁺),ferric ions (Fe³⁺) and hydroxide ions (OH⁻) are dissolved in a molarratio of 1:2:8, is introduced from the one end of the pipe 23 on theside of the metal pipe 23 b by the pumps 14 a and 14 b. In addition, analternating current of a predetermined frequency (e.g., 20 kHz) issupplied from the radiofrequency power source 22 to the inductionheating coil 21, so that an alternating field is formed inside theinduction heating coil 21.

The area (metal pipe) 23 b of the pipe 23, which is formed of aconductive material, is induction-heated by the alternating field formedinside the induction heating coil 21 so as to generate heat, whereby areaction liquid flowing through the pipe 23 is heated up to a reactiontemperature (e.g., 40° C. to 80° C.) by the heat generated by the area23 b formed of a conductive material. Thus, reaction of the reactionliquid is promoted and a coprecipitation reaction between the ferrousions (Fe²⁺) and the ferric ions (Fe³⁺) occurs, whereby magnetite (Fe₃O₄)particles are generated. The thus generated magnetite particles aremoved by a pressure of the reaction liquid flowing through the pipe 23so as to be taken out from the other end of the pipe 23 through the area(resin pipe) 23 a formed of a dielectric material.

When the magnetite particles are generated in the pipe 23, the magnetiteparticles function as a core (magenta core) in the area (resin pipe) 23a formed of a dielectric material. Thus, an inductance of the inductionheating coil 21 increases, so that an impedance of the induction heatingcoil 21 increases. The impedance of the induction heating coil 21 ismeasured by the impedance measuring device 15.

The pump-flowrate deciding unit 16 reads out a measurement result fromthe impedance measuring device 15, and compares the measurement resultwith the previously stored target value.

When the measurement result is equal to or larger than the target value,the flowrate of each of the pumps 14 a and 14 b at this time is decidedas the aforementioned pump flowrate set value.

On the other hand, when the measurement result is smaller than thetarget value, the measurement result is stored in the pump-flowratedeciding unit 16, and the pumps 14 a and 14 b are controlled such thatthe flowrate of the reaction liquid introduced into the the one end ofthe pipe 23 increases.

In principle, as the pump flowrate increases, a generation efficiency ofmagnetite particles also increases until the pump flowrate reaches acertain threshold value. In accordance therewith, the impedance of theinduction heating coil 21 increases (case 1). However, as the pumpflowrate increases after exceeding the threshold value, an unreactedreaction liquid outflows from the other end of the pipe 23, which inturn decreases the generation efficiency of magnetite particles. Inaccordance therewith, the impedance of the induction heating coil 21decreases (case 2).

The pump-flowrate deciding unit 16 reads out a measurement result fromthe impedance measuring device 15, and compares the measurement resultwith the stored previous measurement result.

When the current measurement result is larger than the stored previousmeasurement result, the situation is judged as the case 1, and the pumps14 a and 14 b are controlled such that the flowrate of the reactionliquid introduced to the one end of the pipe 23 gradually increases.During this operation, the pump-flowrate deciding unit 16 successivelyreads out measurement results from the impedance measuring device 15,and compares the measurement results with the previously stored targetvalue. At a time when one of the measurement results becomes the targetvalue or more, the pump-flowrate deciding unit 16 decides each of theflowrates of the pumps 14 a and 14 b as the aforementioned pump flowrateset value.

On the other hand, when the current measurement result is smaller thanthe stored previous measurement result, the situation is judged as thecase 2, and the pumps 14 a and 14 b are controlled such that theflowrate of the reaction liquid introduced to the one end of the pipe 23gradually decreases. During this operation, the ump flow rate decidingunit 16 successively reads out measurement results from the impedancemeasuring device 15, and compares the measurement results with thepreviously stored target value. At a time when one of the measurementresults becomes the target value or more, the pump-flowrate decidingunit 16 decides each of the flowrates of the pumps 14 a and 14 b as theaforementioned pump flowrate set value.

Then, each of the pumps 14 a and 14 b is set such that the reactionliquid is introduced from the one end of the pipe 23 at the pumpflowrate (pump flowrate set value) decided by the pump-flowrate decidingunit 16. Thus, magnetite particles are hereafter generated in the pipe23 at a desired generation efficiency or more corresponding to theimpedance target value previously stored in the pump-flowrate decidingunit 16.

According to the above embodiment, the area 23 b of the pipe 23, whichis formed of a conductive material, is induction-heated by thealternating field inside the induction heating coil 21, and the reactionliquid introduced from the one end of the pipe 23 is heated by the heatgenerated by the area 23 b formed of a conductive material, so that thereaction of the reaction liquid is promoted and thus ferromagneticparticles are generated. When ferromagnetic particles are generated inthe pipe 23, the thus generated ferromagnetic particles function as acore (magnetic core) in the area 23 a of the pipe 23, which is formed ofa dielectric material. Thus, the inductance of the induction heatingcoil 21 increases, so that the impedance of the induction heating coil21 increases. In this case, by measuring the impedance of the inductionheating coil 21, a production efficiency of ferromagnetic particles inthe pipe 23 can be easily estimated from outside.

In addition, according to this embodiment, ferromagnetic particles arecontinuously generated in the pipe 23, without need for stirring thereaction liquid in the reaction container. Thus, the reaction liquid isunlikely to vary in temperature and the mixed condition of the reactionliquid is unlikely to be non-uniform, so that variation of the generatedferromagnetic particles in composition and dimension is small. Inaddition, it is easy to observe the GMP.

In addition, in this embodiment, due to the application of theaforementioned principle of impedance elevation, a production efficiencyof ferromagnetic particles is improved.

That is to say, as the pump flowrate increases, a generation efficiencyof ferromagnetic particles also increases until the pump flowratereaches a certain threshold value. In accordance therewith, theimpedance increases. However, at a pump flowrate beyond the thresholdvalue, an unreacted reaction liquid outflows from the other end of thepipe, which in turn decreases the generation efficiency of ferromagneticparticles. In accordance therewith, the impedance decreases. Thus, inthis embodiment, the pump-flowrate deciding unit 16 decides a pumpflowrate by which the impedance becomes a predetermined value or more.Since the reaction liquid is introduced from the one end of the pipe 23at the flowrate decided by the pump-flowrate deciding unit 16, aproduction efficiency of ferromagnetic particles can be maintained at adesired level or more.

In both the first embodiment and the second embodiment, magnetiteparticles as ferromagnetic particles are generated from an alkalinereaction liquid containing ferrous ions and ferric ions, by means of thecoprecipitation reaction between the ferrous ions and the ferric ions.However, not limited thereto, nickel ferrite particles as ferromagneticparticles may be generated from an alkaline reaction liquid containingferric ions and nickel ions, by means of a coprecipitation reactionbetween the ferric ions and the nickel ions.

In addition, in both the first embodiment and the second embodiment, thepump-flowrate deciding unit 16 decides, as a pump flowrate set value, apump flow rate by which the impedance of the single mode cavity 11 orthe induction heating coil 21 becomes the previously stored target valueor more, based on a measurement result of the impedance measuring device15. However, not limited thereto, a pump flowrate by which the impedanceof the single mode cavity 11 or the induction heating coil 21 becomes amaximum value may be decided as a pump flowrate set value, based on ameasurement result change of the impedance measuring device 15 withrespect to a pump flowrate change. Further, a pump flowrate by which theimpedance of the single mode cavity 11 or the induction heating coil 21becomes a predetermined value or more (e.g., 90% of the maximum value ormore) may be decided as a pump flowrate set value, based on ameasurement result change of the impedance measuring device 15 withrespect to a pump flowrate change.

As described above, the pump-flowrate deciding unit 16 may beconstituted by a computer system, and a program for executing thepump-flowrate deciding unit 16 in the computer system and acomputer-readable storage medium storing the program are also thesubject matter of the present invention.

Furthermore, when the pump-flowrate deciding unit 16 is realized by aprogram (second program) such as OS operated in the computer system, aprogram including various commands for controlling the program such asOS, and a storage medium storing the program are also the subjectmatters of the present invention.

Herein, the storage medium includes one that can be recognized byitself, such as a flexible disc, and a network in which various signalsare transmitted.

-   10 Ferromagnetic-particle manufacturing apparatus-   11 Single mode cavity-   12 Microwave oscillator-   13 Pipe-   14 a Pump-   14 b Pump-   15 Impedance measuring device-   16 Pump-flowrate deciding unit-   17 Coaxial cable-   20 Ferromagnetic-particle manufacturing apparatus-   21 Induction heating coil-   22 Radiofrequency power source-   23 Pipe-   23 a Area formed of dielectric material-   23 b Area formed of conductive material-   24 a Pump-   24 b Pump-   25 Impedance measuring device-   26 Pump-flowrate deciding unit-   27 Radiofrequency cable-   31 First liquid tank-   32 Second liquid tank

1. A ferromagnetic-particle manufacturing apparatus comprising: a singlemode cavity that resonates with a microwave of a predeterminedwavelength; a microwave oscillator electrically connected to the singlemode cavity and configured to introduce the microwave of a predeterminedwavelength into the single mode cavity; a pipe disposed to pass throughan inside of the single mode cavity, the pipe being formed of adielectric material; and a pump configured to introduce, from one end ofthe pipe, an alkaline reaction liquid in which metal ions of aferromagnetic metal and hydroxide ions are dissolved; whereinferromagnetic particles are generated by reacting the reaction liquid.2. The ferromagnetic-particle manufacturing apparatus according to claim1, further comprising: an impedance measuring device configured tomeasure an impedance of the single mode cavity; and a pump-flowratedeciding unit configured to decide, based on a measurement result of theimpedance measuring device, a pump flowrate by which the impedance ofthe single mode cavity becomes a predetermined value or more; whereinthe pump is configured to introduce the reaction liquid at the pumpflowrate decided by the pump-flowrate deciding unit.
 3. Theferromagnetic-particle manufacturing apparatus according to claim 1,wherein an axial length of the pipe is 20 mm to 200 mm.
 4. Aferromagnetic-particle manufacturing apparatus comprising: an inductionheating coil; a radiofrequency power source electrically connected tothe induction heating coil and configured to form an alternating fieldinside the induction heating coil; a pipe disposed to pass through theinside of the induction heating coil, in which at least a partial areaof the pipe in an axial direction thereof is formed of a dielectricmaterial and an area, which is nearer to one end of the pipe than thearea formed of a dielectric material, is formed of a conductivematerial; and a pump configured to introduce, from the one end of thepipe, an alkaline reaction liquid in which metal ions of a ferromagneticmetal and hydroxide ions are dissolved; wherein ferromagnetic particlesare generated by reacting the reaction liquid.
 5. Theferromagnetic-particle manufacturing apparatus according to claim 4,further comprising: an impedance measuring device configured to measurean impedance of the induction heating coil; and a pump-flowrate decidingunit configured to decide, based on a measurement result of theimpedance measuring device, a pump flowrate by which the impedance ofthe induction heating coil becomes a predetermined value or more;wherein the pump is configured to introduce the reaction liquid at thepump flowrate decided by the pump-flowrate deciding unit.
 6. Theferromagnetic-particle manufacturing apparatus according to claim 4,wherein an axial length of the area of the pipe, which is formed of aconductive material, is 20 mm to 200 mm.
 7. The ferromagnetic-particlemanufacturing apparatus according to claim 1, wherein the metal ions ofthe ferromagnetic metal are either or both of iron ions and nickel ions.8. The ferromagnetic-particle manufacturing apparatus according to claim1, wherein sodium hydroxide is dissolved in the reaction liquid.
 9. Theferromagnetic-particle manufacturing apparatus according to claim 1,wherein an internal diameter of the pipe is 0.3 mm to 5.0 mm.
 10. Theferromagnetic-particle manufacturing apparatus according to claim 1,wherein an inner surface of the pipe is treated with a corrosionprotective covering.
 11. (canceled)
 12. (canceled)
 13. Theferromagnetic-particle manufacturing apparatus according to claim 4,wherein the metal ions of the ferromagnetic metal are either or both ofiron ions and nickel ions.
 14. The ferromagnetic-particle manufacturingapparatus according to claim 4, wherein sodium hydroxide is dissolved inthe reaction liquid.
 15. The ferromagnetic-particle manufacturingapparatus according to claim 4, wherein an internal diameter of the pipeis 0.3 mm to 5.0 mm.
 16. The ferromagnetic-particle manufacturingapparatus according to claim 4, wherein an inner surface of the pipe istreated with a corrosion protective covering.